Poor Little Pluto
An article written by a fellow UP Astrosoc member for one of his Journalism classes.
This article is published with permission.
You may visit his blog at http://jonats71421.blogspot.com.
You’ve been team mates for the longest time, all nine of you. You’ve been through a lot together. Ever since you were “discovered” you were a part of the group. You were all inseparable, until one day someone took you off the team because you were just too small. Plus, your little brothers and sisters were always tagging along.
August 24, 2006 was the day Pluto got booted out of our solar system’s official list of planets. We were taught about the nine planets of our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. But in just three days (this was written on August 21, 2008), we will be marking the second year since all science textbooks were rendered obsolete by a vote which involved only 424 of the world’s professional astronomers.
The highly controversial vote on that fateful day capped a long debate on the status of the diminutive erstwhile ninth planet sparked by the discovery of other bodies beyond the orbit of Neptune in the Kuiper Belt.
Okay. Let’s set the issue of Pluto and the vote aside for a while and go on a little “tour” of our solar system just beyond Neptune. For our purposes, let’s hitch a ride on the New Horizons spacecraft –a probe sent by NASA to study Pluto- which is just now past the orbit of Saturn. Let’s imagine that we’re already well on our way to Pluto (which in reality would be in 2015).
Neptune is just a bright blue dot behind us now. Pluto looms ahead in the distance, its single moon, Charon, is just beside it. This is not your normal planetary system, as Pluto and its moon orbit the Sun at a different angle relative to all the other planets. Its orbit also cuts across that of Neptune, so that for part of its 248-year long orbit it actually becomes the eighth planet from the Sun.
We see in front of us a grayish-white globe. Pluto is believed to be composed mostly of ice, a far cry from the rocky inner planets like our very own Earth or the gaseous outer planets like Jupiter or Saturn. It has more in common with comets, so much so that one scientist says that if you knock it off its orbit into the Sun “it would grow a tail and look like a jumbo comet”.
Speaking of comets, this is where some of them come from. As we move past Pluto we encounter a lot of icy objects floating around. We’re now in the Kuiper Belt, a region beyond Neptune where thousands upon thousands of small icy bodies orbit the Sun.
Now we – wait, there’s something big out there. Among the Kuiper Belt objects we soon see a large globe. This is the aptly-named Eris, a body once touted to be the tenth planet from the Sun.
Okay, back to Earth now.
When it was discovered in February 13, 1930, Pluto was considered as the smallest planet in the solar system. Further study showed that there are several moons in our solar system which are much larger. Pluto is so small that both it and its moon would fit within the borders of the continental United States. Astronomers were already wary of this and of this “planet’s” other eccentricities, but Pluto’s status as a planet was only challenged more recently.
Pluto’s status as a planet was first seriously questioned in 1992, when the Kuiper Belt was discovered. Astronomers were asking whether to still consider Pluto a planet, to classify it as a Kuiper Belt object (KBO), or to classify it as both a planet and a KBO . The discovery of Eris in 2005, a body much larger than Pluto, brought to a boil the already simmering debate on Pluto’s classification.
I mentioned before that Eris was “aptly-named”. Indeed it was, as “Eris” was the Greek goddess of discord and strife , and much of that permeated the astronomical community. Many wanted to keep Pluto as a planet, citing cultural and historical reasons. Others kept to the facts, and wanted to demote Pluto to something less than a planet.
Everything came to a head come 2006, when the International Astronomical Union (IAU) started to wrap up its discussions on the matter.
The IAU is an organization of professional astronomers from around the world. Its functions include naming celestial bodies and defining astronomical and physical constants. Basically, this body defines “what is” and “what is not” in Astronomy.
A total of 424 members of the IAU voted to adopt a new definition of the word “planet” on August 24, 2006, effectively dropping Pluto from the original nine planets.
The word “planet” comes from the Greek planetes, meaning “wanderer”. For the longest time that was all that a planet was; a body which “wandered” or orbited around a star. Everything changed with the IAU vote.
Today, a body is considered as a planet only when it fulfills three conditions. It must be:
a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.
The first condition is self-explanatory. The second means that the body in question must be massive enough – that is, have a strong enough gravity – to form a spherical shape. The third condition means that the body must not share its orbit with any other body.
It was the third condition which cost Pluto its planetary status. While it did orbit the Sun, and it did have sufficient gravity to become round, it shared its orbit with a myriad of other objects. Pluto, along with Eris and the other KBOs, was demoted to “dwarf planet” status. However, as of last June, Pluto was relegated to a new class of objects, the so-called “plutoids”.
There you are, along with your brothers and sisters, separated from “the big kids”. You watch them play, knowing that you once joined them in their game. Someone took you out because in their eyes you just didn’t fit in. Don’t worry though. There are others who would love to see you back in the game.
***The footnotes were not transferred to this post. Hehehehe. If you ever have a problem with my sources just send me a personal message at firstname.lastname@example.org and I’ll send you the original document.